Assessing the impact of ancestry genes on women's health

Genetic studies will correlate decreased bone mineral density with African-American, European and East Asian ancestry.

UC Davis researchers are conducting a first-of-its-kind genetic study to determine the importance of ancestry on the development of diseases in women. The research is a follow up to the landmark Women's Health Initiative study, which assessed the long-term benefits of common treatments for preventing heart disease, breast and colorectal cancer and osteoporosis fractures — the most frequent causes of death and poor quality of life in postmenopausal women.

UC Davis was one of 40 sites across the nation that began enrolling women in 1993 for the Women's Health Initiative. Led by John Robbins, professor of medicine, the study included more than 4,000 women aged 50 to 70 from the Sacramento region. Now, UC Davis is one of 12 institutions nationwide to receive a two-year WHI contract from the National Heart, Lung, and Blood Institute to study genetic and biological markers of disease in postmenopausal women.

"This research allows us to identify additional genes that are important in causing diseases that disproportionately affect women or affect them in different ways than men," explained Michael Seldin, principal investigator and chair of the Rowe Program in Human Genetics at UC Davis.

The sheer number and diversity of the women who took part in the WHI study will also allow Seldin and his colleagues to determine the impact of ancestry on disease-risk.

"If we know who is at higher risk, we can individualize our approaches to screening and prevention," said Seldin, who is also professor of biochemistry and medicine.

Using samples taken from WHI participants, the researchers first determine part of each woman's genotype, or genetic fingerprint, using high through-put assays that specifically examine ancestry. They will then correlate this genetic information with phenotypic data — the presence or absence of disease traits. They also are looking for associations between genetic data, observed disease status and ancestry.

The first part of the study includes women who self-identified as African-American or Hispanic. Since individuals in these groups are often of mixed ancestry, Seldin and his colleagues need to determine their continental ancestry — the percent of their genetic make-up that can be attributed to African, European or East Asian ancestry. They then look to see which diseases correlate with ancestry.

The researchers also compare women of African-American or European ancestry to pinpoint the location of genes associated with decreased bone mineral density, a measure of osteoporosis.

"It is well-known that bone mineral density is higher in individuals with a higher percentage of African descent. But, women of African-American descent also get osteoporosis. Including them in the analysis enhances our ability to find the genes we are looking for," he said.

The study also looks at a subset of women identified as being of European descent to determine whether European ancestry puts women at higher risk of hip fracture. Seldin's previous work found that European populations actually represent two genetically distinct Southern and Northern groups.

According to Seldin, the WHI follow-up study allows researchers to get the most out of the original study, which has already provided practical information to women and their physicians about the health benefits of hormone therapy, dietary patterns, calcium/vitamin supplementation on preventing heart disease, cancer and osteoporosis.

"It's a huge resource that promises to help us identify genes important in human disease so that we can work out the basic biochemical and biological basis for disease. This is a unique opportunity to ask additional questions," he said.

Co-investigators include John Robbins and Lihong Qi, an assistant professor in the Rowe Program in Human Genetics.